1. Field of the Invention
The present invention relates to visual examining and sight corrective apparatus, and more particularly to an optical image deflector assembly and method for its use in scanning eyes, locating visually sensitive peripheral areas thereof, and determining corrective prismatic eye glasses adapted to focus light within and along the peripheral edge of the visually sensitive central areas of the eyes for expanding the normal central field of view. More specifically, the invention is directed to prismatic eye glasses and method of making same for persons having retinitis pigmentosa and hemianopia.
2. Description of the Prior Art
U.S. Pat. No. Re. 28,921 discloses an automatic visual sensitivity and blind spot measuring apparatus comprising a device for projecting a spot at different locations on a screen to be viewed by the person being tested along with means for the person to indicate Perception of the spot for subsequent evaluation. The device further comprises means for projecting the spot in different positions in the field of vision of the person being tested.
U.S. Pat. No. 1,990,107 relates to a reflectoscope used in the examination of an eye. The reflectoscope comprises mirrors for reflecting an eye focused image around an operator so that the eye can be observed in the correct orientation to prescribe lenses for correcting refractive disfunctions. The image is reflected onto the normally sensitive portion of the eye.
U.S. Pat. No. 4,264,152 relates to apparatus for moving an image of a target in certain preselected ways to stimulate certain types of eye movements in the subject.
U.S. Pat. No. 4,298,253 relates to apparatus for presenting test images to a viewer at different distances without modifying the visual angle or acuity of the images.
U.S. Pat. No. 3,423,151 relates to auxiliary prismatic lenses mountable on an eye glass frame for use by persons having cataracts. The lenses extend the field of view of the person beyond that provided by ordinary lenses by focusing images beyond the range of the normal lenses onto the pupil of the eye.
U.S. Pat. No. 2,442,849 relates to a method for producing a pair of lenses for providing balanced binocular vision to a greater degree than was previously possible. The invention particularly relates to the correction of conventional disorders such as refractive disorders.
U.S. Pat. No. 4,772,113 relates to eye glasses for improving the vision of people with macular degeneration, optic nerve damage or similar low vision problems, in which their central vision has deteriorated. The eye glasses comprise two lens assemblies, each having a magnifying lens with two convex surfaces and a reducing lens with two concave surfaces. The reducing lens incorporates a prism ring which shifts and focuses a highly intensified light image onto an undamaged peripheral portion of the retina. A disadvantage of these eye glasses is that they are of no value for people suffering from retinitis pigmentose or hemianopia, in which their central vision is good and the peripheral vision is bad, since the shifted image would be focused on a damaged peripheral portion of the retina. Another disadvantage is that the lens do not have a central clear or non-prism area for accommodating the person's good central vision. Also, in those instances where the shifted image would strike the central functional area of the retina, overlapping would occur, resulting in diplopia (double vision).
In addition to the prior art patent literature, an eye disease is known called neovascular senile macular degeneration (N.S.M.D.) in which central vision is greatly impaired, often resulting in blindness by virtue of blood vessels growing into the macula of the eye. The macula controls central vision in the retina, and the rest of the retina is used for peripheral vision. The problem of central vision impairment and blindness due to N.S.M.D. and other problems such as retinitis pigmentosa (tunnel vision) and hemianopia are substantially overcome by the optical image deflector assembly and eye glasses of this invention.
A known eye glass modification intended to expand a person's central field of view for people having retinitis pigmentosa and hemianopia involves the amorphic telescopic lens system, in which one or more telescopes are mounted on each eye glass. The telescopes minify the images so that more information can be seen at one time in the same field. Disadvantages of this form of expanding the field is that multiple images are seen by each eye, and the images are almost twice as small, so that detail is lost. Also, the telescopes extend outwardly a distance from the eye glasses where the force created by the moment of inertia is constantly slipping the spectacles from the nose resting position and falling so that they can be easily damaged. The eye glasses further are not cosmetically appealing, and they are two or more times heavier than normal eye glasses, making them uncomfortable to wear and prone to slip off the wearer's ears due to the force moments generated by the outwardly extending telescopes.
Also known in the prior field expanding art is the use of prisms which are cemented to the temporal edge of the eye glass lenses (base out). The prisms increase a person's efficiency of information processing with reduced fields and normally are not a means for expanding the field. The prisms allow the eye glass wearer to scan the periphery by making small eye movements into the prism to check for objects in the periphery, thereby eliminating the need for inefficient neck movements to accomplish the same task. An exemplary reference of such prism use is disclosed by Dr. Weiss in S, The Optician, Cemented Prism for Severe Field Loss, Volume 163, Jul. 7, 1962. The primary disadvantages of difficulties associated with the use of such prisms are prism blur which may be difficult to tolerate, confusion between frontal and peripheral images, particularly in crowds where people are moving in all directions, diplopia caused by the wearer looking through the edge of the prism, or not suppressing the other eye when one eye is looking through the prism, the necessity for small eye movements into the prism to check for objects in the periphery, resulting in loss of frontal image and a blind spot between the frontal and prism images, prismatic distortions, such as horizontal magnification, curvature of vertical lines, asymmetric horizontal magnification, vertical magnification and change in vertical magnification, with horizontal viewing angle. The prism, when cemented onto the inner surface of the eye glass lens, extends outwardly from the lens and can be hazardous to the eye. The mounting of the prism can be complicated and delicate, due to the lens curvature, and the resulting eye glasses are cosmetically unappealing.
A specialized form of prism known in the art is the fresnel prism. This prism is used for special applications, such as for diagnostic tests. Fresnal prisms are thin sheets of optical plastic composed of multiple prismlets that are pressed into this thin plastic sheet. They are adhered to normal prescription spectacles by capillary action and are subjected to air bubbling during temperature and humidity changes. Fresnel prisms are used in diagnostic and temporary correction and/or preliminary concept of prism requirements for such eye problems as retinitis pigmentosa, strabismus, hemianopia, and macular degeneration, unlike the prescription corrected field expanding glasses herein disclosed, which are clear and transmit or project clear full size images to the retina. The fresnel prisms have poor light transmission and the transmitted or projected images are blurred due to the many prismlets that are pressed into the soft plastic.
The fresnal prisms have a number of other disadvantages. Projection to the retina, especially in crowds as people move in all directions causes multiple images. Double vision results when the right eye looks to the right and the left eye looks through the nasal edge of the left spectacle lens. The multiple prismlets reduce light transmission, which reduces vision and causes night blindness and mobility problems. The multiple prismlets cause many reflections of the same object, especially light bulbs etc., and cause chromatic dispersion. Due to the multiple prismlets, contrast is greatly reduced, and patients are constantly looking through a fine grid. With fresnel prisms the patient must rotate his eye to look into the prism to see the expanded field.
In addition, the fresnel prisms suffer from most of the problems indicated above for prisms generally. In addition, the fresnel prisms suffer from air bubbles when mounted on a surface, are prone to fall off the surface, and subject the viewer to multiple images reflected by the prism rings.
Another known vision-expanding lens in the prior art involves the use of a see-through reflector or mirror, functioning as a beam splitter, mounted on the eye glass frame to extend from the nose at a 45 degree angle to the eye. Disadvantages of this type of vision-expanding lens are that the eye glass user sees two separate images, front and rear, which can be confusing, the mounting of the reflector to the eye glass frame can be complicated and difficult, the reflector extends outwardly from the eye glass lens in an exposed position where it can be readily damaged, and the eye glasses are cosmetically unappealing.
Still another attempt in the prior art to expand the field of view of persons with poor vision involves special high-powered magnifying glasses capable of magnifying an object up to six times, while allowing vision from the side. Disadvantages of this approach are that the eye glasses resemble goggles and protrude nearly three inches from the nose. They must be worn with soft contact lenses, are heavy and cumbersome, and are cosmetically unappealing.
It is clear from the prior art that a strong need exists for eye glasses for expanding the field of view of persons suffering from retinitis pigmentosa and hemianopia without the person suffering the problems and disadvantages of the prior known efforts to expand a person's field of view. This is achieved with the inexpensive, light weight and cosmetically appealing eye glasses of this invention, by refracting images from a field outside the person's normal field of view within and along the peripheral edge of the visually sensitive central functional area of the retina for expanding the central field of view without generating diplopia, distortion and/or blind spots.